(NaturalNews) A supplement of the nutrient quercetin can help make exercise tolerable for adults who battle fatigue and stress, as well as help boost endurance in seasoned exercisers and athletes, according to a new study conducted at the University of South Carolina.
In a trial conducted by Dr J. Mark Davis and colleagues of the Arnold School of Public Health, a group of students who were not regular exercisers were given two 500mg quercetin supplements each day for a week or a placebo. Daily, the exercise endurance and lung capacity of the students was measured by the researchers after a session of riding a stationary bicycle to their maximum capacity. The groups were then reversed for a week and the results compared.
Numbers revealed that in only one week the endurance of those taking quercetin every day had increased by an average of nearly 15%.
"These data suggest that as little as 7 days of quercetin supplementation can increase endurance without exercise training in untrained participants", wrote the authors in a article to be published in International Journal of Sport Nutrition and Exercise Metabolism
Dr Davis and colleagues believe that quercetin could be important not only for regular exercisers and athletes but for improving the condition of individuals with chronic health difficulties who find any physical exertion challenging.
"[Quercetin] may be important in relieving fatigue that keeps (people) sedentary, which is great news for those who often think that they're too tired to exercise
", said Dr Davis in a University of South Carolina press release.
"We believe that this could be a major breakthrough in nutrition." 
Quercetin is a natural compound known as a flavonoid, found abundantly in red apples, red onions, berries, cabbages and broccoli. Little is yet known as to why it may boost exercise endurance
, although early research on animals suggests that the nutrient may increase the number of mitochondria, the energy factories of the body, in brain and muscle cells. Quercetin may also have anti-inflammatory effects; the University of South Carolina team has recently accepted a grant from the National Institutes of Health to examine whether it may be protective against colon cancer.
The current study is not the first to reveal that quercetin
may provide benefits related to exercise and physical stress. Previously, researchers at Appalachian State University conducted a clinical trial with a group of cyclists in order to measure the protective effect the supplement may have on the immune system. The research involved trained cyclists taking 1000mg quercetin daily or a placebo and riding to the point of exhaustion over three hours for three consecutive days. Nearly half of the participants taking a placebo suffered a cold, 'flu or other immune related illness while only 5% of those taking quercetin suffered similarly. 
 Davis et al. The Dietary Flavonoid Quercetin Increases VO2max and Endurance Capacity. International Journal of Sport Nutrition and Exercise Metabolism
. 2009 June. In press.
 Presented at the southeastern regional meeting of the American College of Sports Medicine, Charlotte, N.C., Feb. 8-10 2007.
About the author
Michael Jolliffe is a freelance writer based in Oxford, UK.